I was just in 5546 one and a half weeks ago. I loved this cabin and booked it for our Fantasy cruise in 2013. Now I really can't compare it to the other Cat 4 rooms since I saw none of those. But what I can tell you is that 5546 is not connecting and as a result seems to have much more storage room and our previous cruises inside connecting cabin. The 4E category is much like the cat 5 and 6 categories in the classic ships. (Except somewhat narrower.) There is not small area near the glass door with a chair. The cabin ends at the end of the couch. The extended verandah is worth it's weight in gold! 5546 is on the Starboard side which is where they shoot the fireworks off of. As a result we had a private viewing of the show from our verandah that because of the extension was all the better seen. I invited friends to our room and fit 14 people comfortably in that space. I highly recommend it. As far as the tub goes, it is the Standard square tub. One thing I'd like to add about that, the consensus was, among those I cruised with, that the square tub was better than the round. Another thing I'd like to add about the verandah in 5546. Because of the design of the ship the forward aspect of the verandah is curved as is the aft aspect of 5544 slightly decreasing the privacy of those areas. (i.e. one can see into ones neighbors verandah) At first I thought this would bother me but I quickly realized that everyone above us can see into the extension so the sensation of privacy was an illusion anyway. But this design feature does appear to cut into the size slightly of the extended verandahs. Maybe making my aft neighbors's verandah (5548) slightly more desirable. (although I never heard or seen them on the verandah which makes me think that they probably wasted their money!) I could be wrong on the desirability of the verandah because it appeared that my verandah may have been slightly wider than 5548's. I couldn't tell for sure unless I was on one of the upper deck verandah's looking down which I never had a chance to do.
Just my $.02